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以平均粒径40 nm的W粉为原料,采用“预碳化+二段碳化”的阶段碳化工艺制备出平均粒径为82 nm的近球形WC粉。利用X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、BET比表面积分析仪等测试方法,分别对碳化产物的物相组成、形貌和粒径大小进行表征。研究了不同预碳化温度和二段碳化温度对WC粉粒径和形貌的影响,并对阶段碳化的机制进行了讨论。结果表明,在800~1000℃范围内,WC粉的平均粒径随预碳化温度升高呈先减小后增大的变化趋势,在900℃达到最小值。WC粉的平均粒径随二段碳化温度升高而增大,当二段碳化温度高于1250℃时,WC粉的平均粒径显著增大。碳化过程中WC颗粒的长大主要是由碳化初期纳米W颗粒的烧结合并引起的。低温预碳化能够在W粉颗粒表面形成一定厚度的WC层,阻碍W粉颗粒发生烧结合并,从而有效抑制WC粉的长大。阶段碳化制备纳米WC粉的最佳工艺为:预碳化温度900℃,二段碳化温度1150~1200℃。
The average particle diameter of 40 nm W powder as raw material, the use of “pre-carbonization + two carbonation ” stage carbonization process to prepare an average particle size of 82 nm near-spherical WC powder. The phase composition, morphology and particle size of carbonized products were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and BET specific surface area analyzer. The effects of different pre-carbonization temperature and second-stage carbonization temperature on the particle size and morphology of WC powder were studied. The mechanism of carbonization at the stage was also discussed. The results showed that the average particle size of WC powder decreased first and then increased with the increase of pre-carbonization temperature at 800 ~ 1000 ℃, reaching the minimum at 900 ℃. The mean particle size of WC powder increases with the increase of the second-stage carbonization temperature. When the second-stage carbonization temperature is higher than 1250 ° C, the average particle size of the WC powder increases significantly. The growth of WC particles in the carbonization process is mainly caused by the sintering of the nano-W particles during the initial carbonization. Low-temperature pre-carbonization can form a certain thickness of WC layer on the surface of the W powder particles, which hinders the sintering and combination of the W powder particles, so as to effectively restrain the growth of the WC powder. The optimum conditions for the preparation of nano-WC powder by stage carbonization are: pre-carbonization temperature 900 ℃, second-stage carbonization temperature 1150 ~ 1200 ℃.